It doesn't look like this is currently possible. None of the calls are using any kind of dynamic class loading, it's just hardcoding XenForo_ViewPublic_Helper_Node::functionName(...).

However, for now, you should be able to override XenForo_ViewPublic_Forum_View, XenForo_ViewPublic_Forum_List, and XenForo_ViewPublic_Category_View using the load_class_view event listener. In those three, just replace renderHtml() to use your helper instead of the default one.